Connecting a single-mode fiber to a multimode fiber directly is not feasible due to the differences in their core sizes and the way they propagate light. Single-mode fibers have a small core diameter (around 9 microns) and are designed to carry a single light mode, which allows them to transmit data over long distances with minimal signal loss. In contrast, multimode fibers have a larger core diameter (50 or 62.5 microns) and can carry multiple modes of light, making them suitable for shorter distances

To connect a single-mode fiber to a multimode fiber, you need a media converter. A media converter is a device that converts the optical signal from one type of fiber to another, allowing you to connect devices that would otherwise be incompatible. The media converter will have ports for both single-mode and multimode fibers, and it uses active circuitry to decode and re-encode the optical signals for the different fiber types.

SFP to SFP Media Converter used to convert singlemode to multimode fiber.